Definition of non est factum in English:

non est factum

noun

Law
  • A plea that a written agreement is invalid because the defendant was mistaken about its character when signing it.

    • ‘It is for the person who has signed a document to show that the transaction which it effects is essentially different from the transaction intended so that the signatory can claim non est factum and say that he did not consent to it.’

Origin

Latin, literally ‘it was not done’.

Pronunciation

non est factum

/ˌnɒn ɛst ˈfaktəm/